Measuring server QoS in open virtual worlds: relating QoS to QoE for OpenSim Servers on the Hyper-GRID

Alan Henry David Miller, John Philip McCaffery, Colin Allison, Lisa Dow, Iain Angus Oliver

Research output: Chapter in Book/Report/Conference proceedingConference contribution

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To understand the performance of networked computer
systems it is necessary to consider client, server and
network components. Virtual Worlds are resource intensive
interactive systems. As such they are liable to degradations in
system performance which have a negative impact upon users’
Quality of Experience (QoE). To efficiently use system resources
it is necessary to understand when and how changes in Quality
of Service (QoS) impact upon the QoE. This study investigates
the factors that affect the performance of Open Virtual World
Servers and how these impact upon users. It presents quantitative
experimental results that establish factors which affect QoS
performance and qualitative results of user QoE. The central
research question asks ’to what extent can we identify easily
measurable system properties that will enable us to make efficient
use of server resources whilst preserving QoE?
This paper identifies the Server Frame Time (SFT), the time
taken by the server to create a frame, and Server Frames
per Second (SFPS), the number of frames created by a server
in a second, as key metrics which are easy to measure and
relate directly to QoE. Most virtual world servers are allocated
resources manually and this allocation is independent of the
actual work load. As a result, server resources are under
utilised due to variations in load. This approach causes a higher
provisioning cost than is necessary. The study in this project
establishes a way to determine the usability threshold. Based on
this server resources can be tuned to provide appropriate QoE
for users while making sure that they are utilised to their full
Original languageEnglish
Title of host publicationProceedings of pgNET 2014
Publication statusPublished - 30 Jun 2014


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